The present invention relates to a method for obtaining altitude-related data at locations along roads, in particular while traveling along the roads in a moving vehicle. Such data can be used in vehicle navigation and safety systems.
There are various driver assistance systems for vehicles that help make travel safer and more convenient. For example, one of these driver assistance systems is an adaptive cruise control system that automatically maintains a safe distance between a vehicle and other vehicles or other objects ahead of it. Another driver assistance system is a curve warning system that provides a warning to the vehicle driver if an upcoming curve is being approached too fast and automatically decreases the vehicle speed, if necessary. Another driver assistance system adjusts operation of the vehicle transmission to match the grade of the upcoming road. There are other driver assistance systems in addition to these.
Some of these driver assistance systems use data that represent the road network in the geographic area in which the vehicle is traveling. These data include information about the roads, such as the locations (i.e., geographic coordinates) of the roads and intersections along the roads. The data may also include information about the speed limits along segments of roads, the road curvature, the number of lanes, etc. These road-related data are contained in one or more geographic databases located in the vehicle.
Collecting this kind of road-related data is a significant task. Methods for collecting road-related data are described in U.S. Pat. No. 6,366,851, the entire disclosure of which is incorporated by reference herein. According to an embodiment described in U.S. Pat. No. 6,366,851, a company that produces geographic databases employs technicians (referred to as “researchers”) to physically travel throughout assigned areas in specially equipped vehicles to collect and record information about geographic features for inclusion in and updating of a master copy of a geographic database. Installed in each vehicle is a positioning apparatus, such as a DGPS unit. As the vehicle is driven by a researcher along roads in a geographic area, the positions of the vehicle are determined by the DGPS unit. Data indicating these positions are stored in a data storage device in the vehicle. These positions trace the path of the vehicle and therefore indicate the location and shape of the roads upon which the vehicle has traveled. Other types of road-related data may also be collected by the researchers while the vehicles are being driven along the roads. After the road-related data are collected, the data are analyzed and used to update a master copy of a geographic database.
One type of data that is useful to obtain for use in driver assistance systems and vehicle navigation systems is data that indicate the altitude at points along a road. Data that indicate the altitude at a point can be determined with an altimeter, inclinometer or similar device. Such devices are relatively expensive however. Another consideration with these types of devices is that the data obtained may be noisy due to bouncing in the vehicle environment, i.e., these devices may not have been intended to be used in a moving vehicle. The altitude can also be determined using surveying equipment. However, surveying equipment may require that the equipment be mounted in a stationary position and therefore is not usable in a moving vehicle.
Accordingly, there exists a need for a relatively inexpensive way to determine altitude-related data at various points along a road. Further, there is a need to determine altitude-related data along roads from a moving vehicle.